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Hi, mstrong. I record church music, choral works and loud pipe organ. My WM55 XY mic is useful because it's diminuative enough
not to intrude on the service. It also produces a strong stereo image.

So on my wish list, I would like to achieve more clarity with the choir than I'm currently getting, although that could be a symptom of
coincident mic arrangement. I've not tried spaced mics, as that's a less stealthy approach.

The WM55 is a cardioid which suffers on the low end compared to omnis. Would a larger diaphragm (say 1/2") help with the bass on
a cardioid? Can a larger diaphragm help with the clarity?

I also would like better S/N specs than the Panasonics offer.

Grendel

P.S. Old ladies are the worst about messing with the equipment! They handle the mic and say "What is that?" Maybe if I made it
look like Groucho's mic they'd leave it alone.

Regarding connections on the capsule, i think 3-connections is the
best way to go. Ground, source, and drain. In this case it's easy to
use either linkwitz-mod, or any other powering method. Sennheiser
capsules are made this way, my UEC-14,and probably the DPA 4060 to.




The size of the hole is delicate because it is part of a Helmholtz
resonator!? Thus frequency response suffers when changed.




The AKG CK22 ??(part of a module system) had a "big" diaphragm, but
used a nose-cone to make it "very omnidirectional". A problem all
bigger sized microphones suffer from. (Bad english I know)




/ Per A
















--- In micbuilders@..., Bob Cain <arcane@a...> wrote:

mstrong82 wrote:

You guys want to use 1/2" or bigger.

I want to use 6mm and 9.7 is huge in my application, but if it

were that much

better I would consider it. I'll help you get bigger parts to

play with.

The sole reason for bigger is to reduce self noise. If

noise can be lowered to be in line with the larger capsules

another way that would be great but theory seems to indicate

otherwise.

We all want the same goal and much of what can be experimented

with can

be done with 6mm omni and then applied to larger and different

patterns?

It seems to me some of the list for investigation relates to:

Internal FET choice

Eric B., you still around? Eric did some experiments which,

IIRC, showed that the noise contributed by the FET was

around 6 dB down from the total.

Linkwitz mod built in Y/N

The implication of this, for a two wire capsule, is that you

would not be able to use it with existing "plug-in-power"

applications because it reverses the polarity required. I

still think it better to make it common source by default,

for market considerations, but more easily modifiable to the

source follower configuration than is the WM-60/61.

Larger entry hole Y/N

It would be very interesting to see what the effect of this

is.

RF or not RF

Personally I don't care too much about this. For very small

capsules the benefit would be more to extend the low

frequency response than to reduce noise.

You seem to have eliminated directional capsules from

consideration. Is that correct?

Bob

--

"Things should be described as simply as possible, but no

simpler."

A. Einstein

mstrong82 wrote:

We all want the same goal and much of what can be experimented with can
be done with 6mm omni and then applied to larger and different patterns?

Sorry, I missed this in my last response regarding
directional capsules.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

mstrong82 wrote:

You guys want to use 1/2" or bigger.

I want to use 6mm and 9.7 is huge in my application, but if it were that much
better I would consider it. I'll help you get bigger parts to play with.

The sole reason for bigger is to reduce self noise. If
noise can be lowered to be in line with the larger capsules
another way that would be great but theory seems to indicate
otherwise.

We all want the same goal and much of what can be experimented with can
be done with 6mm omni and then applied to larger and different patterns?

It seems to me some of the list for investigation relates to:

Internal FET choice

Eric B., you still around? Eric did some experiments which,
IIRC, showed that the noise contributed by the FET was
around 6 dB down from the total.

Linkwitz mod built in Y/N

The implication of this, for a two wire capsule, is that you
would not be able to use it with existing "plug-in-power"
applications because it reverses the polarity required. I
still think it better to make it common source by default,
for market considerations, but more easily modifiable to the
source follower configuration than is the WM-60/61.

Larger entry hole Y/N

It would be very interesting to see what the effect of this
is.

RF or not RF

Personally I don't care too much about this. For very small
capsules the benefit would be more to extend the low
frequency response than to reduce noise.

You seem to have eliminated directional capsules from
consideration. Is that correct?


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

ktpbeng wrote:

Plus 48V phantom power is coming from HOT (that's where it
got it's name).

This is NOT correct in a normal XLR connected phantom power scenario!!! The next statement is more correct.

True, my mistake, now that I re-verified it, phantom power is
usually supplied over both: HOT and COLD terminals. Trust but verify.

Indrek

--
Indrek Rebane | Borthwick-Pignon
Electronics Engineer | Tartu Science Park
Phone: (+372) 7 302 641 | Riia 185, 51014 Tartu
Fax: (+372) 7 383 041 | Estonia
indrek@... | www.bps.co.ee

You guys want to use 1/2" or bigger.

I want to use 6mm and 9.7 is huge in my application, but if it were that much
better I would consider it. I'll help you get bigger parts to play with.

We all want the same goal and much of what can be experimented with can
be done with 6mm omni and then applied to larger and different patterns?

It seems to me some of the list for investigation relates to:

Internal FET choice

Linkwitz mod built in Y/N

Larger entry hole Y/N

RF or not RF

Boundary Designs - see
at the bottom is the link for 22 yrs of boundary experiments started by Ken
Warenbrok and Ed Long relatting to PZM and other boundary stuff. This is
GREAT stuff and saves a huge amount of time not replowing already plowed
ground.

It's called mirrorlite, i have links at the office and will find them for you.

Comments interspersed: snippage all over the place...
My apologies, I did not follow this thread from the beginning... it
may not all be on this list! :)
Someone wrote:

Plus 48V phantom power is coming from HOT (that's where it got
it's name).

This is NOT correct in a normal XLR connected phantom power
scenario!!! The next statement is more correct.

An XLR connection, to my understanding, uses a differential
output for noise immunity. That is, there is a "hot" and a
"cold" signal, along with a ground. The hot and cold are
simply negative reciprocals of one another.

so far, so good, but it does not address how phantom power works.
Phantom power works by using the common mode rejection properties of
a balanced line. As such, it puts the 48 volts (in the original
specs of phantom powering)on BOTH the Hot and Cold pins (through
carefully matched 6.8K resistors,IIRC) with the phantom voltage
return on the shield. As such, if you measured across the hot (pin 2
in a normal, industry standard XLR 3pin connection) to the cold (pin
3), you would measure 0 volts, but if you measured from the shield
(pin 1) to either Hot or Cold, you should measure 48V.

There are several ways to connect from single ended to a balanced
line, either through x-formers, op-amps, transistors or even
capacitively... I have seen several schematics on the web, but I do
not have them right in front of me at the moment, so I will have to
post again later.

Good luck!

Bryan

From: "Rich Peet" <richpeet@...>

For my applications I agree a larger diaphragm of 1/2" would be great and going much larger one starts to worry about condensation and humidity in outdoor recordings.
There is a growing number of people that are recording "faint field" and it is the omni's that don't have the proximity effect and it is the figure 8's that are most hard to find.
No one is really marketing a product for this area of recording and what I see dominating the "faint field" right now is the Senn ME 62 condenser, and the MKH 20-P48 which is an RF.
I don't consider my uses to be in the majority but with more people looking at the new digital recorders there is more of a demand for lower noise and higher s/n numbers.

I do nature recording, and would agree in general. However, I'd like to experiment with RF mics with diaphragms larger than 1/2" as well. And various boundary mic designs. Low noise designs are a must.

It makes sense if you are going to the effort to hand make a mic to go for something that competes with the top mics out there. Or is unique enough as to be unavailable. I could certainly use capsules like those in the Sennheiser MKH line. For outdoor conditions those are some of the best for dealing with humidity and so on. I could definitely use a good figure 8 capsule, or one for a multipattern mic.

I don't worry too much about proximity effect. My subjects generally shut up long before I get close enough for that to be any kind of bother.

For outdoor work it's critical to be able to provide good wind and shock protection. This has implications on the mic designs to use, though it does not limit us to any particular polar pattern. It primarily means setups that are compact enough to be protected. One reason why I use M/S stereo.

Walt
wwknapp@...

only about the last point: the sony ecm 907 and others like it have more than an inch of wire from the capsule to the fet; the nakamichi cm 300 i have sitting in front of me has a one and half inch cylinder between the fet and the capsule; it includes a switchable capacity which servers as a 10 db pad. an inch of wire i think we can live with.

umashankar

mstrong82 wrote:

Finally I come back to look at doing this and find the group has

starrted a

migration to a new group within days, maybe hours... PERFECT timing, or
what?

That's just what I thought. :-)

AS FAR AS MAKING THE LINKWITZ MOD Easy, what could be easier than
having it already done? If I recall the capsule part of the mod is

simply

bypassing the internal FET?

No, it is changing the configuration of the internal FET to
source follower from the as-shipped common source mode.
This involves cutting a trace on the little PC board and
making another connection to the can. The problem is that
the solderable tab that allows connection to the tab is a
tiny little thing and so well heat-sunk to the can that
soldering to it can be difficult or even destructive. I use
silver ink to make a low temp connection but others have
objected to the durability of the solution (which I haven't
really found to be a problem.)

How about we make a batch of something a bit better than 60 or 61 with

NO

FET in it in the first place ?

I think that managing the high impedence issues over a
longer connection from diaphragm to an amplifier would be
more than challenging and has strong impact on the noise and
high frequency performance of the result. If there is such
a thing, a better FET might be more appropriate. By
encapsulating it within the near Faraday cage of the can,
induced noise is also minimized.

Frankly, short of better noise performance which seems to be
limited by the small size of the diaphragm I am not sure how
much real improvement is attainable in a device of the size
of the WM-60/61.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

_________________________________________________________________
Marriage? Join BharatMatrimony.com for free.

Andrew Burgess wrote:

it seems that self noise has a large component that is
molecular shot noise from thermally agitated air molecules
impinging on the diaphragm which can only be reduced by
increasing the diaphragm diameter.

Or adding more diaphragms. Two mics, twice the signal, noise
goes up by 1.4.

Right. Either approach begins to degrade high frequency
performance due to coincidence considerations. I'm not sure
which is easier to manage.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

it seems that self noise has a large component that is
molecular shot noise from thermally agitated air molecules
impinging on the diaphragm which can only be reduced by
increasing the diaphragm diameter.

Or adding more diaphragms. Two mics, twice the signal, noise
goes up by 1.4.

mstrong82 wrote:

This is a fit for something I want to make.

I want to make a mic for tracking wildlife. I want to make it so you can hear the
faintest, furthest away sounds. Anotherwords, I want to crank the gain up to
infinity and beyond and I DON'T want to hear transistor hiss.

Ah, but therein lies the rub. From looking at noise specs
for various size mics, from the experiments of one of our
members, and according to:




it seems that self noise has a large component that is
molecular shot noise from thermally agitated air molecules
impinging on the diaphragm which can only be reduced by
increasing the diaphragm diameter. A fairly simple argument
shows that increasing the diameter has the effect of
averaging that noise down relative to the signal.

A definitive experiment would be to compare the self noise
of a small electret at various air pressures, including a
near vacuum, which wouldn't be all that difficult if anyone
had a bell jar and a hand vacuum pump.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

When making larger microphones, I wonder how east it would be to roll your
own? I took a little electret mic apart a few years back but don't recall
exactly what was inside. I do recall that it was very simple and that it
involved some very thin metalized film used as the diaphragm. Could this
film be made available to DIYers? It might also be interesting to
incorporate something like a surface mount OPA134 op amp inside the mic
canister...

mstrong82 wrote:

Anybody here have serious microphone testing capabilities ?

As Jerry Avins in comp.dsp is so fond of saying,
"Engineering is the art of making what you want from what
you have." To that end I have worked out testing and
characterization methods that seem to be repeatable and
accurate. I do my work out of doors, when I can find calm
days, to get a good hemi-anechoic space, use a calibrated
reference mic and fairly sophisticated DSP methods for
compensation of parts of the stimulus and measurement chain
that are less than ideal. I haven't yet taken on the
problem of directional measurement but have given it some
thought.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

mstrong82 wrote:

What you have to realize here is that there are maybe 1,000 of you guys
doing very interesting and creative things with SMALL quantities of ECM's

Personally, I'm fascinated with this. It's my hobby as well as my day job. My
wife says I have no life outside of those little f-in silver cans ;-)

I can't make a dozen of this and a dozen of that. I need to make a minimum of
10,000 of something and know that eventually they will be consumed.

Yes, I understand that the larger you make it, the more
specialized the market becomes. It's just that my interest
has moved beyond tiny but noisy omni's toward much quieter
first order mics that are suitable for coincident stereo or
surround recording. I fully understand that the market size
for such devices is relatively small, as evideneced by the
lack of inexpensive parts for it, but nonetheless I wish to
speak to this type of application and open the door wider to
experimentation in the area.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

mstrong82 wrote:

Finally I come back to look at doing this and find the group has starrted a
migration to a new group within days, maybe hours... PERFECT timing, or
what?

That's just what I thought. :-)

AS FAR AS MAKING THE LINKWITZ MOD Easy, what could be easier than
having it already done? If I recall the capsule part of the mod is simply
bypassing the internal FET?

No, it is changing the configuration of the internal FET to
source follower from the as-shipped common source mode.
This involves cutting a trace on the little PC board and
making another connection to the can. The problem is that
the solderable tab that allows connection to the tab is a
tiny little thing and so well heat-sunk to the can that
soldering to it can be difficult or even destructive. I use
silver ink to make a low temp connection but others have
objected to the durability of the solution (which I haven't
really found to be a problem.)

How about we make a batch of something a bit better than 60 or 61 with NO
FET in it in the first place ?

I think that managing the high impedence issues over a
longer connection from diaphragm to an amplifier would be
more than challenging and has strong impact on the noise and
high frequency performance of the result. If there is such
a thing, a better FET might be more appropriate. By
encapsulating it within the near Faraday cage of the can,
induced noise is also minimized.

Frankly, short of better noise performance which seems to be
limited by the small size of the diaphragm I am not sure how
much real improvement is attainable in a device of the size
of the WM-60/61.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

I am uploading some photos of designs i currently use.
Upload in progress as I have to find some of the photos.
I will get to my electrical designs with time as this is a work in
progress.

1. Clear Channels cheap stereo mic.
2. Its diagram.
This mic was built with all components but the battery embeded in a
sheet of salvage 5/8" lexan plastic. Photo taken before windscreen
and flooding of components with clear epoxy. A hard center, stereo,
pzm design.

3. A photo of me and a modified Greg Clark 32" parabolic. The dish
was designed for bird song recording. Aprox. a 5 degree field of view
and when operated in stereo it is a 10 degree x 5 degree view.
Currently under 12 of these dishes are in use.

4.& 5. Outdoor windscreen based on a commonly available, Shop Vac,
Wet/dry filter element. Great results are being seen up to 30 mph
winds.

6. Football on a stick.
Foam rubber Packed PVC pipe with smaller PVC pipe handle, bat box,
plastic food strainers, single thickness stocking caps, with omnis on
each end.
This mic is used for stereo outdoor night recording when something
non-fragile is needed to throw around a car.

7. Foam Blockhead
My most used stereo boundary. Adjustable center image size by moving
the two omni microphones in and out.

Rich Peet

--- In micbuilders@..., "mstrong82" <mstrong@j...> wrote:

This is a fit for something I want to make.

I want to make a mic for tracking wildlife. I want to make it so

you can hear the

faintest, furthest away sounds. Anotherwords, I want to crank the

gain up to

infinity and beyond and I DON'T want to hear transistor hiss.

I want to use a 6mm mic case and I have 3 volts from batteries to

work with. I

want to use an onmi first.

One problem, IMHO, with the panasonics is the size of the hole in the
front. It is too small and can reverberate under extremely loud sound
pressure levels.

If you can make something with a larger diameter hole it would be great.

Darren

I guess I am the SPAM safeguard right now.

Shortly, the group will be switched to a "restricted membership".
Groups of this type get little or no spam. I will review e-mail
addresses of new members before allowing posts by them. Most spam
sources have addresses that can be somewhat checked against reality.
If "true spam" is posted I will delete that membership and the
message as soon as possible. I will post a message if I delete a
membership so that my actions are accountable to the group. I will
handle in the background memberships not approved but will attempt a
double check of memberships before not approving an address.

I will do what I can regarding spam and all members should do what
they normally do regarding firewalls and blocks. I will try and keep
the group "safe for work and family" but I will not be going to the
length of taking actions regarding members comments and opionions.
I defer that level of activity to the group owner.

Rich Peet

Glad to be rid of the old group -- are safeguards in place to

prevent SPAM

from this one? Is there some specific action that users should do

to

prevent it?

Dick Campbell


Bang-Campbell Associates
3 Water Street PO Box 47
Woods Hole, MA 02543-0047
(T) 508-540-1309 (F) 508-540-8347
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